Hi Dave,



Just to add to what you've said "flux" only re-flow is a very common thing with flip-chip packages and they do behave well from a reliability point of view.



Regards,



Vladimir 



SENTEC

SENTEC

11 Canadian Road, Unit 7.

Scarborough, ON M1R 5G1

Tel: (416) 899-1882

Fax: (905) 882-8812

www.sentec.ca





-----Original Message-----

From: "David D. Hillman" <[log in to unmask]>



Date:         Wed, 3 Jun 2009 16:26:13 

To: <[log in to unmask]>

Subject: Re: [TN] BGA-113 package





Hi Steve and TechNet - I have had a several folks ask me to provide a 

further explanation the " "flux only" will have lower solder joint life 

than a BGA reflowed with solderpaste".  If you look at  many of the solder 

joint life prediction models, you will find that the solder joint height 

has a significant impact on overall solder joint integrity.  Take a look 

at IPC-D-279, Appendix A 3.1, you will find the Engelmaier-Wild model and 

the solder joint height influence is fairly easy to see. If an operator 

reflows a BGA using solder paste, you will get more solder volume and 

therefore a slightly increased solder joint height. With that being said, 

the BGA solder joint life will be better but maybe not necessarily 

required for a product use environment. As many of the TechNet responses 

have shown, it is common practice to use "flux only" reflow and meet the 

requirements of many IPC Class 2/IPC Class 3 use environments with no 

issues. Rockwell Collins has used "flux only' practices for many years and 

is just now transitioning to the new dip-able solderpastes for both 

increased solder joint reliability and ease of rework procedure. Rockwell 

Collins will be publishing a paper on the reliability of BGAs reworked 

with a dip-able solder paste process in the near future. The dip-able 

solder paste is not a new thing - many folks in the wafer bumping 

technology have been using it for years. 



Werner gives a much better explanation of the impact of solder joint 

height than my simple attempt. 



Hope this better explains my comments.



Dave







"Steve Kelly" <[log in to unmask]> 

06/03/2009 03:33 PM



To

<[log in to unmask]>

cc

"'TechNet E-Mail Forum'" <[log in to unmask]>

Subject

RE: [TN] BGA-113 package













Thanks everyone for the excellent feedback. Interesting information. 

Regards Steve Kelly

 

From: [log in to unmask] [mailto:[log in to unmask]] 

Sent: June-03-09 2:50 PM

To: Steve Kelly

Subject: Re: [TN] BGA-113 package

 



Hi Steve! Yes, you can reflow a BGA with "flux only" and not use 

solderpaste. Just remember that solder joint integrity is a function of 

the solder joint height. A BGA reflowed with "flux only" will have lower 

solder joint life than a BGA reflowed with solderpaste. And lower life 

doesn't not necessarily mean bad - just lower. The resulting BGA solder 

joints may be perfectly acceptable for the product use environment. Good 

Luck. 



Dave Hillman 

Rockwell Collins 

[log in to unmask] 





Steve Kelly <[log in to unmask]> 

Sent by: TechNet <[log in to unmask]> 

06/03/2009 11:10 AM 





Please respond to

TechNet E-Mail Forum <[log in to unmask]>; Please respond to

Steve Kelly <[log in to unmask]>







To

[log in to unmask] 

cc



Subject

[TN] BGA-113 package

 

















Hi All,



We have a rigid flex that has a BGA-113 (microstar BGA) package to be

mounted to it. The routing in this area on the top layer leaves me with

.0005 of soldermask clearance from the edge of the BGA pad and .003 

distance

from the edge of the soldermask to the nearest track- in other words I 

have

.0035 of clearance from pad edge to next track assuming a perfect etch and

perfect soldermask registration.



Having rooted around Texas Instruments web site I believe that it may be

possible to reflow this BGA without adding solder paste to the pad - just

letting the ball collapse do the attachment. If my scenario is correct I

could open up the soldermask and not have too many concerns about bridging

between the BGA pads and the tracks. Any thoughts or comments would be

appreciated.



Thanks Steve Kelly 







Steve Kelly (PLEASE NOTE NEW E-MAIL ADDRESS)



(416) 750-8433 (work)



(416) 750-0016 (fax)



(416) 577-8433 (cell)









---------------------------------------------------

Technet Mail List provided as a service by IPC using LISTSERV 15.0

To unsubscribe, send a message to [log in to unmask] with following text in

the BODY (NOT the subject field): SIGNOFF Technet

To temporarily halt or (re-start) delivery of Technet send e-mail to 

[log in to unmask]: SET Technet NOMAIL or (MAIL)

To receive ONE mailing per day of all the posts: send e-mail to 

[log in to unmask]: SET Technet Digest

Search the archives of previous posts at: http://listserv.ipc.org/archives

Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 

for additional information, or contact Keach Sasamori at [log in to unmask] or 

847-615-7100 ext.2815

-----------------------------------------------------



---------------------------------------------------

Technet Mail List provided as a service by IPC using LISTSERV 15.0

To unsubscribe, send a message to [log in to unmask] with following text in

the BODY (NOT the subject field): SIGNOFF Technet

To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)

To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest

Search the archives of previous posts at: http://listserv.ipc.org/archives

Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815

-----------------------------------------------------